2025年7月29日下午场托福写作完整版答案及解析（含范文）

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　主题：cactus如何到达非洲

　　Birds

　　The first theory is that the wicker cactus was spread like many other plants: by birds. Its seeds could have been eaten by a migrating bird, which stored them in its digestive tract and then passed them on as waste after crossing to another continent. In a suitable environment on the new continent, the plants could have developed from these transported seeds and then reproduced. This theory is supported by the fact that many bird species are known to make regular migrations of great distances.

　　First, about birds spreading seeds. Well, some birds do eat the seeds of the wicker cactus. The cactus produces small white fruits with the seeds inside them. And some species of birds eat the fruit and spread its seeds through their digestion. The problem is that none of these bird species typically fly directly across the Atlantic ocean, from the Americas to Africa. There are other birds that cross the Atlantic ocean and travel from the Americas to Africa regularly. But those birds mainly eat insects and fish, they typically don't feed on fruit. So they probably would not consume wicker cactus seeds.

　　Predates separation of continents

　　A second theory is that the wicker cactus has existed for so long that it is actually older than the ocean that now separates Africa and South America. Long ago, Africa and South America were part of one giant continent. In this explanation, the wicker cactus first evolved during the ancient time before the continents separated. As the two land masses slowly drifted apart over millions of years, early wicker cactus plants were left on each side of the ocean.

　　The idea that the wicker cactus evolved before the continent separated has been called into question. You see, until recently, no one knew exactly when cactus species first evolved. But researchers can now study the DNA or genes of a species to estimate how long this species has existed. And new DNA studies suggest that no cactus existed when south America and Africa were connected in one giant continent. Based on the DNA studies, scientists now believe that all cactus species, including the wicker cactus, first evolved much later. Millions of years after the separation of continents.

　　Sailors

　　The third theory is that sixteenth-century sailors carried the wicker cactus from South America to Africa on their boats. Records show that when Portuguese and Spanish sailors traveled to the Americas, they frequently brought plants back and forth across the ocean. Since the wicker cactus can survive for a long time without soil, it could have easily lived through such a trip.

　　Third, the sailor theory. If sailors had carried the wicker cactus to Africa on boats, we would expect to find it growing, mostly in places where ships would have arrived. Near ports. But the wicker practice usually grows in parts of Africa that are far away from ports and not in any of Africa’s port cities. What's more, some of the places where the cactus is found are very far. Deep in the middle of the African continent. In areas, ships could never even approach.

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　主题：prairie dog是否应该被保护

　　First, cattle farmers have long argued that prairie dogs should not be protected, because they are agricultural pests. The farmers point out that prairie dogs compete with cattle for grass that cattle graze on. Prairie dogs live in large groups that build networks of burrows underground and feed on the grass above their burrows. The farmers have argued that the loss of grass to prairie dogs creates a real economic problem for them.

　　First, the idea that the prairie dogs are serious tests is outdated. It originated in the early nineteen hundreds, and it makes sense at that time, but nowadays most of the cows raised in the US do not get their food by grazing freely on the grassland but by being fed processed feed in closed feeding areas. Grass is no longer as precious resource for cattle farmers as it once was. Furthermore, some studies indicate that prairie dog activities actually make the soil in the grasslands more fertile. So the presence of prairie dogs is actually beneficial to the growth of the glasses.

　　Second, prairie dogs may represent a serious health hazard, since they often become infected with plague, a dangerous bacterial disease that can infect people as well. Like many rodents, prairie dogs carry fleas, insects that can transmit the plague bacteria from prairie dogs to humans.

　　Second, it's extremely rare for plague to actually spread from prairie dogs to humans. One reason for this is that the type of flea that lives on the bodies of prairie dogs does not tend to live on human bodies. So the transmission of the plague by flees to humans is extremely unlikely. Let me give you some figures to illustrate how rare it is. In the state of Colorado , only ten people were infected with plagues who contacted with the prairie dogs in the last fifteen years.

　　Third, some people argue that prairie dogs do not have enough ecological importance to deserve special protection. According to this argument, it makes much more ecological sense to protect species at the top of the food chain-meat eaters such as wolves or bears-because those animals have a large impact on the balance of the whole ecosystem. Plant eaters like the prairie dogs have a more limited impact, and protecting them would not make much difference to the broader ecosystem.

　　Third, prairie dogs do play an important ecological role even though they are just plant eaters. For example, the underground borrows that prairie dogs create present an important habitat for other species. Animals like salamanders and snakes live in those burrows. Also, prairie dogs are a critical food service for dozens of predators. Foxes, coyotes and some rare species of predators as well. So the continued loss of prairie dogs would have a negative impact on many species in the prairie ecosystems.

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　主题：尼加拉瓜运河和巴拿马运河的优缺点

　　First, a canal through Nicaragua would facilitate faster transport of goods between Asia and the East Coast of the United States. Ships coming from Asia have to travel farther south to reach the Panama Canal than they would to reach a canal in Nicaragua. Building a canal through Nicaragua would cut about 500 nautical miles off the journey between Asia and the East Coast of the United States.

　　It is true that the distance that ships would have to cover on the open seas between Asia and the east coast of the united states would be significantly reduced. But the problem is that ships going through the garigue would have to spend more time passing through the canal itself. That's because the country of Nicaragua is much wider than Panama. In fact, A canal built across Nicaragua would be more than three times longer than the Panama canal. Ships moving through a canal move very slowly. And so any time gained by ships and covering less distance on the open seas would be lost in passing through the near or canal itself.

　　Second, a canal through Nicaragua could allow for the transit of larger ships. As global trade over long distances grows in importance, shipping companies may try to increase efficiency by constructing larger freighter ships. The Panama Canal can handle ships carrying up to approximately 13,000 containers of goods. A canal through Nicaragua could be designed to accommodate ships that can carry several thousand more containers of goods at a time.

　　It is not clear that a canal in Nicaragua could consistently allow for larger ships to pass through. For this to happen, water levels in all parts of the canal need to be relatively. Currently, proposals for the canal include building it through lake Nicaragua, the largest lake in the region. But during droughts, the water level of lake Nicaragua becomes very low, and low water levels in lake Nicaragua naming that sometimes the water level will be too low for larger shirts to pass through.

　　Third, a canal through Nicaragua would be an opportunity to improve the environment. The builders of the canal have committed to compensate for environmental disruption caused by construction. For example, in order to offset the removal of trees in the path of the canal, the builders have agreed to plant a large number of trees in areas disrupted by the construction. In addition, they are also planning to replace trees in areas of Nicaragua where deforestation is already an extensive problem. These efforts to repair environmental damage will make significant improvements to the land.

　　Reforestation will not likely be enough to compensate for all the disruption caused by building the canal across Nicaragua. Nicar. Is an ecologically diverse country with several different types of ecosystems. And almost all of them will be altered by the construction of the canal. For example, the area affected by the canal construction contains different types of. Each with its own distinct ecosystem. Much diversity. To effectively measure the harm done to the environment and nearly impossible to repair the damage.

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　主题：rideshare的优缺点

　　First, rideshare companies argue that increased use of ride-sharing can reduce traffic in cities. When rides are easily available through rideshare services, city residents are less likely to buy cars. This results in fewer cars on city streets and less congestion throughout these cities. Reducing the amount of traffic on city streets benefits everyone, since it allows people to get to their destinations more quickly.

　　Yes, fewer people may feel the need to own cars because of the availability of ride shares, but this doesn't mean that traffic will be reduced. Regular car owners use their cars only to get to their destinations. They drive to work in the morning park, the car, and in the evening, they return home. So they only use their cars during short peak times. However, ride share drivers spend additional time on the road. After they drop a passenger off, they have to drive to another place to pick up someone else and so on. Driving the car from place to place while looking for passengers adds to the usual car traffic. So the expansion of rice sharing might lead to more traffic in cities, not less.

　　Moreover, rideshare companies state that they can provide an alternative to public transportation options, such as trains and buses. This is especially important in locations that are far from transit centers or where transit routes do not efficiently connect different parts of a city. People who live in communities with inefficient public transportation systems can have easier commutes if the availability of ride-sharing increases.

　　Secondly, having an unlimited number of ride share cars can hurt public transportation systems. Since ride shares provide an alternative to public transportation in many neighborhoods. They can discourage city governments from investing in improvements to public transportation. Ride shares result in fewer people using public transportation. And this discourages city governments from funding better train and bus systems. And with less funding. Train and bus lines will never extend to serve all the neighborhoods.

　　Finally, rideshare companies provide a great deal of employment. Tens of thousands of people work for these companies as drivers. If cities allow more cars to be used as rideshares, more jobs will be created. Increasing the amount of transportation available also allows people to work in locations that otherwise might be too distant or costly to commute to. So, ride-sharing improves a city's job market for both drivers and their passengers.

　　And finally. What about the idea that expanding ride shares will create better employment opportunities? Well, in fact. Unlimited ride sharing will probably reduce the pay of every ride share driver. You see, there are only a limited number of customers each day. And if the number of ride share drivers increases. Well, this doesn't mean that the number of customers will increase. If there are more rideshare drivers that they serve the same limited number of customers. Each driver will, on average, get fewer paying customers, and earn the less money. That's why many current ride share drivers oppose the expansion of ride sharing. Summarize the points made in the letter, being sure to explain how they challenge the specific arguments made in the reading passage.

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　主题：iron fertilization的利弊

　　First, iron fertilization may not be very effective. So far, only very few experiments have shown that iron fertilization leads to increased absorption of atmospheric CO2 by phytoplankton. In addition, the increases in CO2 absorption detected in the experiments were quite small. This leads many experts to think that full-scale iron fertilization would be just as ineffective.

　　It's true that iron fertilized phytoplankton in the experiments. Did not absorb a lot of carbon dioxide. However, these studies are unconvincing. Because they were too short. Most of them lasted less than a month. But it turns out that phytoplankton plants live for two or three months and absorb most carbon dioxide in the last month of their lives. So phytoplankton may not be efficient absorbers of CO two during the first month. But the efficiency would probably greatly increase in the second and third month.

　　Second, the quick growth of phytoplankton can lead to dangerous increases in environmental toxins. Some phytoplankton produce toxins that are relatively harmless in small amounts but can be very dangerous when produced by a large enough population. The toxins kill some species of fish, which hurts the fishing industry. They also cause other species of fish to be poisonous for human consumption, which causes many people to become sick. If we implement iron fertilization, we can expect this to happen much more often.

　　It's true that phytoplankton may occasionally produce too many environmental toxins in certain areas. But this problem can be easily addressed if we just stop fertilizing those areas with. If we stop fertilizing the areas, the phytoplankton will not have enough nutrition and will quickly start dying. As a result, the production of the toxins will quickly decline and there will be no permanent.

　　Third, seeding the oceans with large volumes of a nutrient such as iron could upset the oceans' ecological balance. We do not know how the various ocean organisms will react to an iron-rich environment. Some may thrive in it, while others may suffer. In the long run, iron fertilization could change the plant and animal composition of the ocean ecosystems; some species may even become extinct as a result.

　　Finally, it's true that we don't really know the long-term effects of iron fertilization on ocean ecosystem. But this is a risk we may have to take, because if we don't, we will be facing a much greater risk. The rapid changes to earth's climate will probably cause much greater harm to the ocean ecosystems than iron fertilization ever. We have to act now in a big way to reduce carbon dioxide if we want to slow climate change. And iron fertilization is one of our best bets at succeeding